C++ OpenGL正方形和箭头

我试图创建一个正方形，在上面我创建了一个箭头。它就像一个2D米，类似的东西。但我不知道如何在正方形顶部创建箭头

int count = 1;
for (float y = 1; y < 11; y++) {
    y1 = y1 - 0.51;
    y2 = y2 - 0.51;

    float x2 = -2.0;
    for (float x1 = -2.5; x1 < 2.5; x1 = x1 + 0.51) {

        glColor3f(windy[count], 1.0, 0.0);
        glVertex2f(x1, y1);
        glVertex2f(x1, y2);
        glVertex2f(x2, y2);
        glVertex2f(x2, y1);
        count = count + 1;
        x2 = x2 + 0.51;



    }
}

glutSwapBuffers();
glEnd(); //End the glBegin Function

---

为什么在调用

glEnd（）

之前要交换缓冲区：

int count = 1;
for (float y = 1; y < 11; y++) {
    y1 = y1 - 0.51;
    y2 = y2 - 0.51;

    float x2 = -2.0;
    for (float x1 = -2.5; x1 < 2.5; x1 = x1 + 0.51) {

        glColor3f(windy[count], 1.0, 0.0);
        glVertex2f(x1, y1);
        glVertex2f(x1, y2);
        glVertex2f(x2, y2);
        glVertex2f(x2, y1);
        count = count + 1;
        x2 = x2 + 0.51;
    }
}

//glutSwapBuffers(); // wrong place
glEnd(); //End the glBegin Function
glutSwapBuffers(); // Must be after draw operation

int count=1；
用于（浮动y=1；y<11；y++）{
y1=y1-0.51；
y2=y2-0.51；
浮动x2=-2.0；
对于（浮点x1=-2.5；x1<2.5；x1=x1+0.51）{
glColor3f（风[计数]，1.0,0.0）；
glVertex2f（x1，y1）；
glVertex2f（x1，y2）；
glVertex2f（x2，y2）；
glVertex2f（x2，y1）；
计数=计数+1；
x2=x2+0.51；
}
}
//glutSwapBuffers（）；//错误的地方
格伦德（）//结束glBegin函数
glutSwapBuffers（）；//必须在牵引操作后进行

要在形状的顶部绘制箭头，必须更加：

int count = 1;
for (float y = 1; y < 11; y++) {
    y1 = y1 - 0.51;
    y2 = y2 - 0.51;

    float x2 = -2.0;
    for (float x1 = -2.5; x1 < 2.5; x1 = x1 + 0.51) {

        glColor3f(windy[count], 1.0, 0.0);
        glVertex2f(x1, y1);
        glVertex2f(x1, y2);
        glVertex2f(x2, y2);
        glVertex2f(x2, y1);
        count = count + 1;
        x2 = x2 + 0.51;
    }
}

//glutSwapBuffers(); // wrong place
glEnd(); //End the glBegin Function

// draw arrow
glBegin(GL_LINE_LOOP);//start drawing a line loop
        glVertex3f(-1.0f, 0.0f, 0.0f);//left of window
        glVertex3f(0.0f, -1.0f, 0.0f);//bottom of window
        glVertex3f(1.0f, 0.0f, 0.0f);//right of window
        glVertex3f(0.0f, 1.0f, 0.0f);//top of window
        glEnd();//end drawing of line loo


// atlast we can swap our buffers
glutSwapBuffers(); // Must be after draw operation

int count=1；
用于（浮动y=1；y<11；y++）{
y1=y1-0.51；
y2=y2-0.51；
浮动x2=-2.0；
对于（浮点x1=-2.5；x1<2.5；x1=x1+0.51）{
glColor3f（风[计数]，1.0,0.0）；
glVertex2f（x1，y1）；
glVertex2f（x1，y2）；
glVertex2f（x2，y2）；
glVertex2f（x2，y1）；
计数=计数+1；
x2=x2+0.51；
}
}
//glutSwapBuffers（）；//错误的地方
格伦德（）//结束glBegin函数
//拔箭
glBegin（GL_线_环）//开始画一个直线循环
glVertex3f（-1.0f，0.0f，0.0f）//窗口左侧
glVertex3f（0.0f，-1.0f，0.0f）//窗底
glVertex3f（1.0f，0.0f，0.0f）//窗口右侧
glVertex3f（0.0f，1.0f，0.0f）//窗顶
格伦德（）//loo线端图
//至少我们可以交换缓冲区
glutSwapBuffers（）；//必须在牵引操作后进行

你不应该在

glBegin

和

glEnd

@Java\u新手：我的答案帮你了吗？@Java\u新手：我的答案帮你了吗？

int count = 1;
for (float y = 1; y < 11; y++) {
    y1 = y1 - 0.51;
    y2 = y2 - 0.51;

    float x2 = -2.0;
    for (float x1 = -2.5; x1 < 2.5; x1 = x1 + 0.51) {

        glColor3f(windy[count], 1.0, 0.0);
        glVertex2f(x1, y1);
        glVertex2f(x1, y2);
        glVertex2f(x2, y2);
        glVertex2f(x2, y1);
        count = count + 1;
        x2 = x2 + 0.51;
    }
}

//glutSwapBuffers(); // wrong place
glEnd(); //End the glBegin Function

// draw arrow
glBegin(GL_LINE_LOOP);//start drawing a line loop
        glVertex3f(-1.0f, 0.0f, 0.0f);//left of window
        glVertex3f(0.0f, -1.0f, 0.0f);//bottom of window
        glVertex3f(1.0f, 0.0f, 0.0f);//right of window
        glVertex3f(0.0f, 1.0f, 0.0f);//top of window
        glEnd();//end drawing of line loo


// atlast we can swap our buffers
glutSwapBuffers(); // Must be after draw operation